- NAME
- SYNOPSIS
- DESCRIPTION

- Methods
- Functions

- RETURN VALUES
- COPYRIGHT

# NAME

EVP_PKEY_meth_new, EVP_PKEY_meth_free, EVP_PKEY_meth_copy, EVP_PKEY_meth_find, EVP_PKEY_meth_add0, EVP_PKEY_METHOD, EVP_PKEY_meth_set_init, EVP_PKEY_meth_set_copy, EVP_PKEY_meth_set_cleanup, EVP_PKEY_meth_set_paramgen, EVP_PKEY_meth_set_keygen, EVP_PKEY_meth_set_sign, EVP_PKEY_meth_set_verify, EVP_PKEY_meth_set_verify_recover, EVP_PKEY_meth_set_signctx, EVP_PKEY_meth_set_verifyctx, EVP_PKEY_meth_set_encrypt, EVP_PKEY_meth_set_decrypt, EVP_PKEY_meth_set_derive, EVP_PKEY_meth_set_ctrl, EVP_PKEY_meth_get_init, EVP_PKEY_meth_get_copy, EVP_PKEY_meth_get_cleanup, EVP_PKEY_meth_get_paramgen, EVP_PKEY_meth_get_keygen, EVP_PKEY_meth_get_sign, EVP_PKEY_meth_get_verify, EVP_PKEY_meth_get_verify_recover, EVP_PKEY_meth_get_signctx, EVP_PKEY_meth_get_verifyctx, EVP_PKEY_meth_get_encrypt, EVP_PKEY_meth_get_decrypt, EVP_PKEY_meth_get_derive, EVP_PKEY_meth_get_ctrl - manipulating EVP_PKEY_METHOD structure

# SYNOPSIS

     #include <openssl/evp.h>

     typedef struct evp_pkey_method_st EVP_PKEY_METHOD;

     EVP_PKEY_METHOD *EVP_PKEY_meth_new(int id, int flags);
     void EVP_PKEY_meth_free(EVP_PKEY_METHOD *pmeth);
     void EVP_PKEY_meth_copy(EVP_PKEY_METHOD *dst, const EVP_PKEY_METHOD *src);
     const EVP_PKEY_METHOD *EVP_PKEY_meth_find(int type);
     int EVP_PKEY_meth_add0(const EVP_PKEY_METHOD *pmeth);

     void EVP_PKEY_meth_set_init(EVP_PKEY_METHOD *pmeth,
                                 int (*init) (EVP_PKEY_CTX *ctx));
     void EVP_PKEY_meth_set_copy(EVP_PKEY_METHOD *pmeth,
                                 int (*copy) (EVP_PKEY_CTX *dst,
                                              EVP_PKEY_CTX *src));
     void EVP_PKEY_meth_set_cleanup(EVP_PKEY_METHOD *pmeth,
                                    void (*cleanup) (EVP_PKEY_CTX *ctx));
     void EVP_PKEY_meth_set_paramgen(EVP_PKEY_METHOD *pmeth,
                                     int (*paramgen_init) (EVP_PKEY_CTX *ctx),
                                     int (*paramgen) (EVP_PKEY_CTX *ctx,
                                                      EVP_PKEY *pkey));
     void EVP_PKEY_meth_set_keygen(EVP_PKEY_METHOD *pmeth,
                                   int (*keygen_init) (EVP_PKEY_CTX *ctx),
                                   int (*keygen) (EVP_PKEY_CTX *ctx,
                                                  EVP_PKEY *pkey));
     void EVP_PKEY_meth_set_sign(EVP_PKEY_METHOD *pmeth,
                                 int (*sign_init) (EVP_PKEY_CTX *ctx),
                                 int (*sign) (EVP_PKEY_CTX *ctx,
                                              unsigned char *sig, size_t *siglen,
                                              const unsigned char *tbs,
                                              size_t tbslen));
     void EVP_PKEY_meth_set_verify(EVP_PKEY_METHOD *pmeth,
                                   int (*verify_init) (EVP_PKEY_CTX *ctx),
                                   int (*verify) (EVP_PKEY_CTX *ctx,
                                                  const unsigned char *sig,
                                                  size_t siglen,
                                                  const unsigned char *tbs,
                                                  size_t tbslen));
     void EVP_PKEY_meth_set_verify_recover(EVP_PKEY_METHOD *pmeth,
                                           int (*verify_recover_init) (EVP_PKEY_CTX
                                                                       *ctx),
                                           int (*verify_recover) (EVP_PKEY_CTX
                                                                  *ctx,
                                                                  unsigned char
                                                                  *sig,
                                                                  size_t *siglen,
                                                                  const unsigned
                                                                  char *tbs,
                                                                  size_t tbslen));
     void EVP_PKEY_meth_set_signctx(EVP_PKEY_METHOD *pmeth,
                                    int (*signctx_init) (EVP_PKEY_CTX *ctx,
                                                         EVP_MD_CTX *mctx),
                                    int (*signctx) (EVP_PKEY_CTX *ctx,
                                                    unsigned char *sig,
                                                    size_t *siglen,
                                                    EVP_MD_CTX *mctx));
     void EVP_PKEY_meth_set_verifyctx(EVP_PKEY_METHOD *pmeth,
                                      int (*verifyctx_init) (EVP_PKEY_CTX *ctx,
                                                             EVP_MD_CTX *mctx),
                                      int (*verifyctx) (EVP_PKEY_CTX *ctx,
                                                        const unsigned char *sig,
                                                        int siglen,
                                                        EVP_MD_CTX *mctx));
     void EVP_PKEY_meth_set_encrypt(EVP_PKEY_METHOD *pmeth,
                                    int (*encrypt_init) (EVP_PKEY_CTX *ctx),
                                    int (*encryptfn) (EVP_PKEY_CTX *ctx,
                                                      unsigned char *out,
                                                      size_t *outlen,
                                                      const unsigned char *in,
                                                      size_t inlen));
     void EVP_PKEY_meth_set_decrypt(EVP_PKEY_METHOD *pmeth,
                                    int (*decrypt_init) (EVP_PKEY_CTX *ctx),
                                    int (*decrypt) (EVP_PKEY_CTX *ctx,
                                                    unsigned char *out,
                                                    size_t *outlen,
                                                    const unsigned char *in,
                                                    size_t inlen));
     void EVP_PKEY_meth_set_derive(EVP_PKEY_METHOD *pmeth,
                                   int (*derive_init) (EVP_PKEY_CTX *ctx),
                                   int (*derive) (EVP_PKEY_CTX *ctx,
                                                  unsigned char *key,
                                                  size_t *keylen));
     void EVP_PKEY_meth_set_ctrl(EVP_PKEY_METHOD *pmeth,
                                 int (*ctrl) (EVP_PKEY_CTX *ctx, int type, int p1,
                                              void *p2),
                                 int (*ctrl_str) (EVP_PKEY_CTX *ctx,
                                                  const char *type,
                                                  const char *value));

     void EVP_PKEY_meth_get_init(EVP_PKEY_METHOD *pmeth,
                                 int (**pinit) (EVP_PKEY_CTX *ctx));
     void EVP_PKEY_meth_get_copy(EVP_PKEY_METHOD *pmeth,
                                 int (**pcopy) (EVP_PKEY_CTX *dst,
                                                EVP_PKEY_CTX *src));
     void EVP_PKEY_meth_get_cleanup(EVP_PKEY_METHOD *pmeth,
                                    void (**pcleanup) (EVP_PKEY_CTX *ctx));
     void EVP_PKEY_meth_get_paramgen(EVP_PKEY_METHOD *pmeth,
                                     int (**pparamgen_init) (EVP_PKEY_CTX *ctx),
                                     int (**pparamgen) (EVP_PKEY_CTX *ctx,
                                                        EVP_PKEY *pkey));
     void EVP_PKEY_meth_get_keygen(EVP_PKEY_METHOD *pmeth,
                                   int (**pkeygen_init) (EVP_PKEY_CTX *ctx),
                                   int (**pkeygen) (EVP_PKEY_CTX *ctx,
                                                    EVP_PKEY *pkey));
     void EVP_PKEY_meth_get_sign(EVP_PKEY_METHOD *pmeth,
                                 int (**psign_init) (EVP_PKEY_CTX *ctx),
                                 int (**psign) (EVP_PKEY_CTX *ctx,
                                                unsigned char *sig, size_t *siglen,
                                                const unsigned char *tbs,
                                                size_t tbslen));
     void EVP_PKEY_meth_get_verify(EVP_PKEY_METHOD *pmeth,
                                   int (**pverify_init) (EVP_PKEY_CTX *ctx),
                                   int (**pverify) (EVP_PKEY_CTX *ctx,
                                                    const unsigned char *sig,
                                                    size_t siglen,
                                                    const unsigned char *tbs,
                                                    size_t tbslen));
     void EVP_PKEY_meth_get_verify_recover(EVP_PKEY_METHOD *pmeth,
                                           int (**pverify_recover_init) (EVP_PKEY_CTX
                                                                         *ctx),
                                           int (**pverify_recover) (EVP_PKEY_CTX
                                                                    *ctx,
                                                                    unsigned char
                                                                    *sig,
                                                                    size_t *siglen,
                                                                    const unsigned
                                                                    char *tbs,
                                                                    size_t tbslen));
     void EVP_PKEY_meth_get_signctx(EVP_PKEY_METHOD *pmeth,
                                    int (**psignctx_init) (EVP_PKEY_CTX *ctx,
                                                           EVP_MD_CTX *mctx),
                                    int (**psignctx) (EVP_PKEY_CTX *ctx,
                                                      unsigned char *sig,
                                                      size_t *siglen,
                                                      EVP_MD_CTX *mctx));
     void EVP_PKEY_meth_get_verifyctx(EVP_PKEY_METHOD *pmeth,
                                      int (**pverifyctx_init) (EVP_PKEY_CTX *ctx,
                                                               EVP_MD_CTX *mctx),
                                      int (**pverifyctx) (EVP_PKEY_CTX *ctx,
                                                          const unsigned char *sig,
                                                          int siglen,
                                                          EVP_MD_CTX *mctx));
     void EVP_PKEY_meth_get_encrypt(EVP_PKEY_METHOD *pmeth,
                                    int (**pencrypt_init) (EVP_PKEY_CTX *ctx),
                                    int (**pencryptfn) (EVP_PKEY_CTX *ctx,
                                                        unsigned char *out,
                                                        size_t *outlen,
                                                        const unsigned char *in,
                                                        size_t inlen));
     void EVP_PKEY_meth_get_decrypt(EVP_PKEY_METHOD *pmeth,
                                    int (**pdecrypt_init) (EVP_PKEY_CTX *ctx),
                                    int (**pdecrypt) (EVP_PKEY_CTX *ctx,
                                                      unsigned char *out,
                                                      size_t *outlen,
                                                      const unsigned char *in,
                                                      size_t inlen));
     void EVP_PKEY_meth_get_derive(EVP_PKEY_METHOD *pmeth,
                                   int (**pderive_init) (EVP_PKEY_CTX *ctx),
                                   int (**pderive) (EVP_PKEY_CTX *ctx,
                                                    unsigned char *key,
                                                    size_t *keylen));
     void EVP_PKEY_meth_get_ctrl(EVP_PKEY_METHOD *pmeth,
                                 int (**pctrl) (EVP_PKEY_CTX *ctx, int type, int p1,
                                                void *p2),
                                 int (**pctrl_str) (EVP_PKEY_CTX *ctx,
                                                    const char *type,
                                                    const char *value));

# DESCRIPTION

EVP_PKEY_METHOD is a structure which holds a set of methods for a specific public key cryptographic algorithm. Those methods are usually used to perform different jobs, such as generating a key, signing or verifying, encrypting or decrypting, etc.

There are two places where the EVP_PKEY_METHOD objects are stored: one is a built-in static array representing the standard methods for different algorithms, and the other one is a stack of user-defined application-specific methods, which can be manipulated by using EVP_PKEY_meth_add0(3).

The EVP_PKEY_METHOD objects are usually referenced by EVP_PKEY_CTX objects.

## Methods

The methods are the underlying implementations of a particular public key algorithm present by the EVP_PKEY_CTX object.

     int (*init) (EVP_PKEY_CTX *ctx);
     int (*copy) (EVP_PKEY_CTX *dst, EVP_PKEY_CTX *src);
     void (*cleanup) (EVP_PKEY_CTX *ctx);

The `init()` method is called to initialize algorithm-specific data when a new EVP_PKEY_CTX is created. As opposed to init(), the `cleanup()` method is called when an EVP_PKEY_CTX is freed. The `copy()` method is called when an EVP_PKEY_CTX is being duplicated. Refer to EVP_PKEY_CTX_new(3), EVP_PKEY_CTX_new_id(3), EVP_PKEY_CTX_free(3) and EVP_PKEY_CTX_dup(3).

     int (*paramgen_init) (EVP_PKEY_CTX *ctx);
     int (*paramgen) (EVP_PKEY_CTX *ctx, EVP_PKEY *pkey);

The `paramgen_init()` and `paramgen()` methods deal with key parameter generation. They are called by EVP_PKEY_paramgen_init(3) and EVP_PKEY_paramgen(3) to handle the parameter generation process.

     int (*keygen_init) (EVP_PKEY_CTX *ctx);
     int (*keygen) (EVP_PKEY_CTX *ctx, EVP_PKEY *pkey);

The `keygen_init()` and `keygen()` methods are used to generate the actual key for the specified algorithm. They are called by EVP_PKEY_keygen_init(3) and EVP_PKEY_keygen(3).

     int (*sign_init) (EVP_PKEY_CTX *ctx);
     int (*sign) (EVP_PKEY_CTX *ctx, unsigned char *sig, size_t *siglen,
                  const unsigned char *tbs, size_t tbslen);

The `sign_init()` and `sign()` methods are used to generate the signature of a piece of data using a private key. They are called by EVP_PKEY_sign_init(3) and EVP_PKEY_sign(3).

     int (*verify_init) (EVP_PKEY_CTX *ctx);
     int (*verify) (EVP_PKEY_CTX *ctx,
                    const unsigned char *sig, size_t siglen,
                    const unsigned char *tbs, size_t tbslen);

The `verify_init()` and `verify()` methods are used to verify whether a signature is valid. They are called by EVP_PKEY_verify_init(3) and EVP_PKEY_verify(3).

     int (*verify_recover_init) (EVP_PKEY_CTX *ctx);
     int (*verify_recover) (EVP_PKEY_CTX *ctx,
                            unsigned char *rout, size_t *routlen,
                            const unsigned char *sig, size_t siglen);

The `verify_recover_init()` and `verify_recover()` methods are used to verify a signature and then recover the digest from the signature (for instance, a signature that was generated by RSA signing algorithm). They are called by EVP_PKEY_verify_recover_init(3) and EVP_PKEY_verify_recover(3).

     int (*signctx_init) (EVP_PKEY_CTX *ctx, EVP_MD_CTX *mctx);
     int (*signctx) (EVP_PKEY_CTX *ctx, unsigned char *sig, size_t *siglen,
                     EVP_MD_CTX *mctx);

The `signctx_init()` and `signctx()` methods are used to sign a digest present by a EVP_MD_CTX object. They are called by the EVP_DigestSign functions. See EVP_DigestSignInit(3) for detail.

     int (*verifyctx_init) (EVP_PKEY_CTX *ctx, EVP_MD_CTX *mctx);
     int (*verifyctx) (EVP_PKEY_CTX *ctx, const unsigned char *sig, int siglen,
                       EVP_MD_CTX *mctx);

The `verifyctx_init()` and `verifyctx()` methods are used to verify a signature against the data in a EVP_MD_CTX object. They are called by the various EVP_DigestVerify functions. See EVP_DigestVerifyInit(3) for detail.

     int (*encrypt_init) (EVP_PKEY_CTX *ctx);
     int (*encrypt) (EVP_PKEY_CTX *ctx, unsigned char *out, size_t *outlen,
                     const unsigned char *in, size_t inlen);

The `encrypt_init()` and `encrypt()` methods are used to encrypt a piece of data. They are called by EVP_PKEY_encrypt_init(3) and EVP_PKEY_encrypt(3).

     int (*decrypt_init) (EVP_PKEY_CTX *ctx);
     int (*decrypt) (EVP_PKEY_CTX *ctx, unsigned char *out, size_t *outlen,
                     const unsigned char *in, size_t inlen);

The `decrypt_init()` and `decrypt()` methods are used to decrypt a piece of data. They are called by EVP_PKEY_decrypt_init(3) and EVP_PKEY_decrypt(3).

     int (*derive_init) (EVP_PKEY_CTX *ctx);
     int (*derive) (EVP_PKEY_CTX *ctx, unsigned char *key, size_t *keylen);

The `derive_init()` and `derive()` methods are used to derive the shared secret from a public key algorithm (for instance, the DH algorithm). They are called by EVP_PKEY_derive_init(3) and EVP_PKEY_derive(3).

     int (*ctrl) (EVP_PKEY_CTX *ctx, int type, int p1, void *p2);
     int (*ctrl_str) (EVP_PKEY_CTX *ctx, const char *type, const char *value);

The `ctrl()` and `ctrl_str()` methods are used to adjust algorithm-specific settings. See EVP_PKEY_CTX_ctrl(3) and related functions for detail.

     int (*digestsign) (EVP_MD_CTX *ctx, unsigned char *sig, size_t *siglen,
                        const unsigned char *tbs, size_t tbslen);
     int (*digestverify) (EVP_MD_CTX *ctx, const unsigned char *sig,
                          size_t siglen, const unsigned char *tbs,
                          size_t tbslen);

The `digestsign()` and `digestverify()` methods are used to generate or verify a signature in a one-shot mode. They could be called by EVP_DigetSign(3) and EVP_DigestVerify(3).

## Functions

`EVP_PKEY_meth_new()` creates and returns a new EVP_PKEY_METHOD object, and associates the given id and flags. The following flags are supported:

     EVP_PKEY_FLAG_AUTOARGLEN
     EVP_PKEY_FLAG_SIGCTX_CUSTOM

If an EVP_PKEY_METHOD is set with the EVP_PKEY_FLAG_AUTOARGLEN flag, the maximum size of the output buffer will be automatically calculated or checked in corresponding EVP methods by the EVP framework. Thus the implementations of these methods don't need to care about handling the case of returning output buffer size by themselves. For details on the output buffer size, refer to EVP_PKEY_sign(3).

The EVP_PKEY_FLAG_SIGCTX_CUSTOM is used to indicate the `signctx()` method of an EVP_PKEY_METHOD is always called by the EVP framework while doing a digest signing operation by calling EVP_DigestSignFinal(3).

`EVP_PKEY_meth_free()` frees an existing EVP_PKEY_METHOD pointed by pmeth.

`EVP_PKEY_meth_copy()` copies an EVP_PKEY_METHOD object from src to dst.

`EVP_PKEY_meth_find()` finds an EVP_PKEY_METHOD object with the id. This function first searches through the user-defined method objects and then the built-in objects.

`EVP_PKEY_meth_add0()` adds pmeth to the user defined stack of methods.

The EVP_PKEY_meth_set functions set the corresponding fields of EVP_PKEY_METHOD structure with the arguments passed.

The EVP_PKEY_meth_get functions get the corresponding fields of EVP_PKEY_METHOD structure to the arguments provided.

# RETURN VALUES

`EVP_PKEY_meth_new()` returns a pointer to a new EVP_PKEY_METHOD object or returns NULL on error.

`EVP_PKEY_meth_free()` and `EVP_PKEY_meth_copy()` do not return values.

`EVP_PKEY_meth_find()` returns a pointer to the found EVP_PKEY_METHOD object or returns NULL if not found.

`EVP_PKEY_meth_add0()` returns 1 if method is added successfully or 0 if an error occurred.

All EVP_PKEY_meth_set and EVP_PKEY_meth_get functions have no return values. For the 'get' functions, function pointers are returned by arguments.

# COPYRIGHT

Copyright 2017 The OpenSSL Project Authors. All Rights Reserved.

Licensed under the OpenSSL license (the ``License''). You may not use this file except in compliance with the License. You can obtain a copy in the file LICENSE in the source distribution or at https://www.openssl.org/source/license.html.